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Beach glass, river rocks, and dune sands all form the same way

Researchers have discovered that the smooth texture of beach glass, river rocks, and dune sands is formed in the exact same way. Despite the diversity of these particles, they are all rounded in the process of colliding with other particles.

Study lead author Douglas J. Jerolmack is a geophysicist at the University of Pennsylvania.

“We show that wind-blown sand, river pebbles, and wave-worked pebbles all round in the same way by colliding,” said Jerolmack. “And, more important, we show how nature selects for the conditions that lead to this universal behavior.”

The research team combined lab experiments and field measurements with mathematical models for their investigation into how particles round.

The models used in the study were created to prove the Poincare conjecture, a breakthrough in pure mathematics that was formulated around the turn of the 20th century. The researchers found that the same equations used in these mathematical models represent natural shape evolution as well.

By identifying a universal way that particles round, scientists can now reconstruct the history of other particles. The research may also enable scientists to track the small pieces of sediment that chip off of larger particles. These tiny scraps ultimately build beaches, floodplains, and wetlands.

The research team demonstrated how simple geometry predicts a common shape evolution for most sediments. Whether they were blowing in the wind or being tossed around in the ocean or river, collisions with other particles caused all of the particles to round in an identical manner.

As a result of the research, the scientists now have the mathematical tools they need to reconstruct the transport history of any particle based on its shape. This will allow experts to more accurately forecast how landscapes will change over time.

The study is published in in the journal Science Advances.

By Chrissy Sexton, Staff Writer

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